Despite general meade's victory at the battle of gettysburg, why did president lincoln appoint grant as the new general to lead the union army?

Because he has failed to destroy Lee's army

Explanation:

Despite Meade was leading his army into victory during the bloodiest battle of the Civil War, he was criticized  from President Abraham Lincoln because according to him he failed to destroy Lee’s battered army, which had escaped across the Potomac River. This could have been stopped, according to Lincoln.

an unexpected salary cut

b. 155 enlisted men and no officers